Process for the production of boric acid.



UNITED STATES T OFFICE.

ALFRED BURGER, OF NEW BRIGHTON, NEW YORK.

PROCESS FOR THE PRODUCTIGN OF BORIC ACID.

Specification of Letters Patent.

1,108,129. No Drawing. 1

To all whom it may ccnr-ern Be it known that I, ALFRED Brianna, a citizen of Switzerland, and a resident of Yew Brighton, in the county of Richmond and State of New York, have invented cer tain new and useful Improvements in Processes for the Production of Boric Acid, of which the following is a specifiZ-ation.

My invention has for its object, a new and useful process for the production of boric acid and comprises generally the treatment of the products obtainable by calcining borates or boric-acid-containing minerals with corbon dioxid. By borates I means those minerals and earth-allmli-boratcs containing boric acid in such a form or combination that it can be eliminated.therefrom by treatment with carbon dioxid, among which are colemanite, boronatrocalcite and pandermite.

I have found that whereas the production of boric acid by the action of carbon dioxid upon the borates in their natural condition, results in-small yields, the necessity of enormous quantities of weak solutions of the acid and the expense incident to the evaporation of large amounts of water, boric acid can be produced much more easily and economically by first calcining the borates before treatment with carbon dioxid, by which process larger. yields are obtained, smaller quantities of water are necessary, the strength of the acid solutions is materially increased and the amount of water to be evaporated is very greatly reduced. My process not only" reduces the cost of. boric acid obtainable from high grade borates. but also allows of its successful commercial production from low grade minerals which are not suitablefor use in the present known processes.

When borates in their natural condition containing water of crystallization are treated with carbon dioxid in the presence dioxid. In using colemanite, the solution l contains only about 4% of boric'acid, practically allof which remains in solution and does not separate out to any extent, thus necessitating the handling and evaporation Patented Aug. 25, 191a.

Application filed January 22, 1914. Serial No. 8.13.645.

The reaction upon the calcined products takes place much more rapidly than upon the uncalcined b orates thus causing a saving in labor or expense incident to manufacture.

It would seem that the calcining of the borates, not only drives off the water of crystallization, but that it also converts the original borateinto bodies more readily at tacked by the carbon dioxid. It is probably that metaborates and tetraborates are formed, the calcium compounds of these being formed when colemanite is employed.

By treatment of these compounds with carbon dioxid gas there results a mixture of free boric acid and acid-calcium-borates and from the latter the boric acid may be recovered by any suitable means but I prefer submit it to a grinding operation. The mixture is introduced into a suitable autoclave or closed receptacle and carbon dioxid gas is introduced under a pressure of about 100 lbs. The t mperature should be maintained at about 50 C. I l hen the operation is com plete, which usually requires'about g} of an hour, the mixture is filtered to remove the calcium carbonate, and hydrochloric acid slowly added to the filtrate until itshows slight acidity as indicated by methyl orange. The whole is then allowed to cool, and the precipitated boric acid removed by filtration.

The solution contains some boric acid and calcium chlorid and can be used again to moisten the colemanite in the first operation, or the boric acid may be recovered from it by any suitable means. Acids other than sulfate L nation.

without pressure time 15 am; tem'ru 1 promuztlon 01 cammmg :1 bmram 21141 pmdncs with (:zu'bmi Maxim Le herein des rucepr pl'mhlctlon of born wii'h carbon Ciiotiu, gas ie dumll bfi 0011s Kill *1 hmtx mineral and, bone 101d.

X 12 pmduced 

